Method of using radial thrust elements to re-enter a previously-installed tubular in a lateral

ABSTRACT

A method of re-entering a previously-installed tubular in a lateral borehole from a primary borehole connected to the lateral borehole includes passing a downhole tool from the primary borehole into the lateral borehole, activating one or more radial thrust elements proximate to a nose portion of the downhole tool to apply a radial thrust to the downhole tool and lift the nose portion into alignment with the tubular, and inserting the nose portion of the downhole tool into the tubular.

BACKGROUND OF THE INVENTION

The invention relates generally to multilateral well operations. Moreparticularly, the invention relates to a method and apparatus foraccessing a branch of a multilateral well.

A multilateral well, also known as a multi-branch well, is a well havingone or more lateral boreholes branching off a single primary wellbore.The primary wellbore may be vertical, horizontal, or deviated. Thelateral boreholes may branch off the primary wellbore in any number ofdirections to allow production from several target reservoirs orformations through the primary wellbore. Multilateral wells areadvantageous in comparison to single wells in that their lateralboreholes can be brought into close contact with several targetreservoirs, thereby allowing production from the reservoirs to bemaximized.

Tubulars are often installed in lateral boreholes. For example, inunconsolidated or weakly consolidated formations, liners are ofteninstalled in lateral boreholes to prevent the boreholes from collapsing.After such installation, it is often desirable to re-enter the tubularin order to perform one or more operations in the lateral borehole. Suchre-entry operations generally include inserting a downhole tool into thetubular. In some cases, there may be eccentricity between the tubularand the lateral borehole, for example, due to formation washout. In thiscase, there is the likelihood that a downhole tool inserted into thelateral borehole would be misaligned with the tubular and may not beable to enter the tubular or may even become stuck in between thetubular and the lateral borehole.

From the foregoing, a method of assuring entry of a downhole tool into atubular in a lateral borehole would be useful.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a method of re-entering apreviously-installed tubular in a lateral borehole from a primaryborehole connected to the lateral borehole. The method comprises passinga downhole tool from the primary borehole into the lateral borehole,activating one or more radial thrust elements proximate to a noseportion of the downhole tool to apply a radial thrust to the downholetool and lift the nose portion into alignment with the tubular, andinserting the nose portion of the downhole tool into the tubular. In oneembodiment, activating the one or more radial thrust elements comprisesradially extending one or more bow springs coupled to the downhole tool.In another embodiment, activating the one or more radial thrust elementscomprises radially extending one or more plugs coupled to the downholetool. In yet another embodiment, activating the one or more radialthrust elements comprises generating one or more hydraulic jets from thedownhole tool.

In another aspect, the invention relates to a downhole tool forre-entering a previously-installed tubular in a lateral borehole of amultilateral well. The downhole tool comprises a downhole tool bodysized for insertion into the tubular and one or more radial thrustelements proximate to a nose portion of the downhole tool body andoperable to apply a radial thrust to the downhole tool body and lift thenose portion into alignment with the tubular.

Other features and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, described below, illustrate typicalembodiments of the invention and are not to be considered limiting ofthe scope of the invention, for the invention may admit to other equallyeffective embodiments. The figures are not necessarily to scale, andcertain features and certain view of the figures may be shownexaggerated in scale or in schematic in the interest of clarity andconciseness.

FIG. 1 is a schematic of a multilateral well in which a tubularinstalled in a lateral borehole is eccentric with the lateral borehole.

FIG. 2A is an example of a downhole tool for re-entering a tubular thatis eccentric with a lateral borehole.

FIG. 2B shows the downhole tool of FIG. 2A aligned for entry with thetubular.

FIG. 2C shows a method of radially extending the bow springs of FIG. 2A.

FIG. 3A is another example of a downhole tool for re-entering a tubularthat is eccentric with a lateral borehole.

FIGS. 3B and 3C illustrate a partial cross-section of the aligningmechanism of FIG. 3A and a method of radially extending the plugs ofFIG. 3A.

FIGS. 3D and 3E illustrate a partial cross-section of the aligningmechanism of FIG. 3A and an alternate method of radially extending theplugs of FIG. 3A.

FIGS. 4A and 4B depict another example of a downhole tool forre-entering a tubular that is eccentric with a lateral borehole.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described in detail with reference to a fewpreferred embodiments, as illustrated in the accompanying drawings. Indescribing the preferred embodiments, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that theinvention may be practiced without some or all of these specificdetails. In other instances, well-known features and/or process stepshave not been described in detail so as not to unnecessarily obscure theinvention. In addition, like or identical reference numerals are used toidentify common or similar elements.

FIG. 1 illustrates an example of a multilateral well 100 in which themethod and apparatus of the invention may be employed. The multilateralwell 100 includes a primary borehole 102 and a lateral borehole 104branching off the primary borehole 102. The multilateral well 100 mayhave one or more lateral boreholes. Casing 106 may be installed in theprimary borehole 102 and may include a window 107 through which thelateral borehole 104 can be accessed, in a manner well known in the art.A tubular 108 has been installed in the lateral borehole 104, in amanner well known in the art. For example, the tubular 108 may be aliner, such as a slotted or perforated liner, installed in the lateralborehole 104 to prevent the lateral borehole 108 from collapsing. Thetubular 108 includes a bore (not shown) for receiving a downhole tool110 at the end of a tool string 112. In the illustrated example, thetubular 108 is eccentric with the lateral borehole 104. This may be due,for example, to formation washout at 114. Also, the downhole tool 110 isnot aligned for entry with the tubular 108. In accordance with theinvention, a downhole tool is provided with an aligning mechanism tofacilitate entry of the downhole tool into the tubular 108. In general,the aligning mechanism includes radial thrust elements proximate to thenose portion of the downhole tool. The radial thrust elements can beactivated to apply radial thrust to the downhole tool which would liftthe nose of the downhole tool into alignment with the tubular.

FIG. 2A shows an example of a downhole tool 200 having an elongateddownhole tool body 202 with a rear portion 201 and nose portion 203. Thedownhole tool 200 is adapted to facilitate entry into a tubular in alateral borehole when the tubular is eccentric with the lateralborehole, more specifically when the nose portion 203 is not aligned forentry into the tubular. The tool body 202 is sized for insertion intothe target tubular 108. In one example, the nose portion 203 of the toolbody 202 includes a tubular sealing element 204 for sealing engagementwith a sealing surface, such as a sealing bore of a tubular. The rearportion 201 may also include additional sealing elements 205 for sealingengagement with a sealing surface. In this example, the nose portion 203includes a nozzle 206 with orifices 207 for fluid circulation when thesealing elements 204, 205 are in the sealing position. However, it isnot necessary that the downhole tool 200 includes the nozzle 206.Further, any suitable means of conveying the downhole tool 200 into thelateral borehole, such as a string of pipes or wireline, may be coupledto the rear portion 201 of the downhole tool 200.

The downhole tool 200 includes an aligning mechanism 208 disposedbetween the rear portion 201 and the nose portion 203. In this example,the aligning mechanism 208 includes a sleeve 210 coupled to the noseportion 203. A plurality of radial thrust elements 212 are mounted in aspaced relation about a circumference of the sleeve 210. Alternatively,the radial thrust elements 212 may be provided on only a portion of thecircumference of the sleeve 210, such as the portion of the sleeve 210that would be adjacent to the bottom of the lateral borehole. In oneexample, the radial thrust elements 212 are radially extendible bowsprings. One of the ends of the bow springs 212 is fixed to the sleeve210 while the other of the ends of the bow springs 212 is attached to asleeve 214 that is concentric with and slidable over the sleeve 210. Thebow springs 212 are in a retracted (or flat) position, as shown in FIG.2A, until they are actuated or activated. To align the nose portion 203with the tubular 108, the bow springs 212 are actuated or activated suchthat the bow springs 212 become radially extended (or bow out). FIG. 2Bshows the bow springs 212 radially extended away from the sleeve 210upon actuation. The radially extended bow springs 212 apply a radialthrust which lifts the nose portion 203 of the downhole tool 200 andmaintains the nose position 203 in a lifted position, thereby aligningthe nose portion 203 for entry into the tubular 108.

The aligning mechanism 208 includes a mechanism for actuating oractivating the bow springs 212. The actuation mechanism may take on anysuitable form known in the art. The actuation mechanism may bemechanical, hydraulic, or electrical. In one example, a compressionspring 216 is mounted between the rear portion 201 and sleeve 210 andarranged to exert a force on the sleeve 214. A load applied to thecompression spring 216, which overcomes the force of the compressionspring 216, would move the sleeve 214 axially relative to the sleeve210, thereby moving the movable ends of the bow springs 212 axially andradially extending the bow springs 212. In another example, asillustrated in FIG. 2C, a hydraulic cylinder 218 may be mounted betweenthe rear portion 201 and sleeve 210, and the piston 220 of the hydrauliccylinder 218 may apply the force needed to move the sleeve 214 axiallyto radially extend the bow springs 212. Pressurized fluid can besupplied to the hydraulic cylinder 218 through the bore of the tool body202 from the surface or a suitable location downhole. In another examplenot illustrated, the movable ends of the bow springs 212 may be coupledto the sleeve 210 by pin/slot connections, and movement of the pinswithin the slots can be controlled by a motor or other means, which maybe mechanical, hydraulic, or electrical, to actuate the bow springs 212.

In FIG. 3A, an alternate aligning mechanism 300 is coupled to the noseportion 203 of the downhole tool 200. The aligning mechanism 300includes a sleeve 302 which carries radial thrust elements 304. In thisexample, the radial thrust elements 304 are depicted as plugs ormandrels 304 distributed about a circumference of the sleeve 302.Alternatively, the plugs 304 may be provided on only a portion of thecircumference of the sleeve 302, such as the portion of the sleeve 302that would be adjacent to the bottom of the lateral borehole. Referringto FIG. 3B, the plugs 304 are inserted in apertures 306 in the sleeve302 and are slidable within the apertures 306. The plugs 304 areinitially maintained in a retracted position, for example, by means of aspring 308. When the force of the spring 308 is overcome, the plugs 304radially extend outwardly, i.e., away from the sleeve 302, as shown inFIG. 3C. In the same manner indicated for the bow springs (212 in FIG.2B), in the radially extended position, the plugs 304 lift the noseportion (203 in FIG. 3A) of the downhole tool (200 in FIG. 3A) andfacilitate entry of the downhole tool into the tubular (108 in FIG. 2A).Any suitable mechanism may be used to radially extend the plugs 304. Forexample, FIGS. 3B and 3C depict an inflatable element 312 that may beinserted into the sleeve 302 and then inflated to apply a radial forceto the plugs 304. The applied force would overcome the force of thesprings 308, thereby radially extending the plugs 304. Alternatively, asdepicted in FIGS. 3D and 3E, a mandrel 313 may be used to apply a radialforce to the plugs 304 to thereby radially extend the plugs 304. Thediameter of the mandrel 313 controls radial extension of the plugs 304.In FIGS. 3B-3E, any other suitable mechanism besides springs 308, suchas J-slot connections, may be used to control radial extension of theplugs 304.

In FIGS. 4A and 4B, a different aligning mechanism 400 is coupled to thedownhole tool 200. The aligning mechanism 400 includes a sleeve 402coupled to the nose portion 203 and the rear portion 201 of the downholetool 200. Orifices 404 are formed in the sleeve 402. The orifices 404are distributed about a circumference of the sleeve 402. The orifices404 are used to create hydraulic jets, which provide the radial thrustthat will lift the nose portion 203 of the downhole tool 200 foralignment and entry into the tubular. In this case, the orifices 404 forcreating the hydraulic jets are part of the radial thrust elements.Typically, only the orifices 404 located on one side of the sleeve 402are left open. In other words, the orifices 404 on the side opposite tothe intended displacement to achieve alignment are typically plugged. InFIG. 4B, the plugged orifices 404 are not shown. If necessary, theorientation of the downhole tool 200 can be adjusted such that theunplugged orifices 404 are in the orientation to provide the intendeddisplacement of the nose portion 203. Pressure buildup inside the toolbody 202 to create the hydraulic jets can be achieved by mechanisms suchas ball drop or choke/flow restriction. For example, a ball can bedropped into the tool body 202 to seal off the orifices 207 at the noseportion 203 of the downhole tool 200. Then, hydraulic fluid can bepumped down the bore of the tool body 202 and forced through theorifices 404 to create hydraulic jets 405 that would lift the noseportion 203 into alignment for entry into the tubular 108.

A method of re-entering a tubular (108 in FIG. 1) in a lateral borehole(104 in FIG. 1) from a primary borehole (102 in FIG. 1) includes passinga downhole tool (200 in FIGS. 2A, 3A, 4A) from the primary borehole intothe lateral borehole, where the downhole tool is equipped with radialthrust elements. The downhole tool may be lowered through casing in theprimary wellbore and passed into the lateral borehole through a windowin the casing. In general, any suitable method known in the art forlocating the lateral borehole and orienting the downhole tool so that itcan pass into the lateral borehole from the primary borehole can beused. The method further includes activating the radial thrust elementsto lift the nose of the downhole tool into alignment with the tubular inthe lateral borehole. Any suitable technique for activating the radialthrust elements, such as those described above, may be used. Once thenose portion of the downhole tool is aligned with the tubular, the noseportion of the downhole tool can be inserted into the tubular. Theradial thrust elements can then be de-activated to allow the downholetool to be fully inserted into the tubular. De-activation is generallythe reverse of the process used in activating the radial thrustelements.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

1. A method of re-entering a previously-installed tubular in a lateralborehole from a primary borehole connected to the lateral borehole,comprising: passing a downhole tool from the primary borehole into thelateral borehole; activating one or more radial thrust elementsproximate to a nose portion of the downhole tool to apply a radialthrust to the downhole tool and lift the nose portion into alignmentwith the tubular; and inserting the nose portion of the downhole toolinto the tubular.
 2. The method of claim 1, wherein activating the oneor more radial thrust elements comprises radially extending one or morebow springs coupled to the downhole tool.
 3. The method of claim 2,wherein the bow springs are mounted on a sleeve coupled to the noseportion and radially extending the one or more bow springs comprisesaxially moving one of the ends of the bow springs relative to thesleeve.
 4. The method of claim 1, wherein activating the one or moreradial thrust elements comprises radially extending one or more plugscoupled to the downhole tool.
 5. The method of claim 4, wherein theplugs are inserted in apertures provided in a sleeve coupled to the noseportion and extending the one or more plugs comprises inserting a toolinto a bore of the sleeve and operating the tool to apply a radial forceto the one or more plugs.
 6. The method of claim 1, wherein activatingthe one or more radial thrust elements comprises generating one or morehydraulic jets from the downhole tool.
 7. The method of claim 6, whereingenerating the one or more hydraulic jets comprises forcing fluidthrough one or more orifices in the downhole tool.
 8. The method ofclaim 1, further comprising de-activating the radial thrust elementsafter inserting the nose portion of the downhole tool into the tubular.9. The method of claim 1, wherein passing the downhole tool from theprimary borehole to the lateral borehole comprises lowering the downholetool into the primary borehole.
 10. The method of claim 1, wherein thepreviously-installed tubular is eccentric with the lateral borehole. 11.A downhole tool for re-entering a previously-installed tubular in alateral borehole of a multilateral well, comprising: a downhole toolbody sized for insertion into the previously-installed tubular; and oneor more radial thrust elements proximate to a nose portion of thedownhole tool body and operable to apply a radial thrust to the downholetool body and lift the nose portion into alignment with the tubular. 12.The downhole tool of claim 11, wherein the radial thrust elements aredisposed between the nose portion and a rear portion of the downholetool body.
 13. The downhole tool of claim 11, wherein the radial thrustelements comprise one or more radially extendible bow springs.
 14. Thedownhole tool of claim 11, wherein the radial thrust elements compriseone or more radially extendible plugs.
 15. The downhole tool of claim11, wherein the radial thrust elements comprise one or more orifices forgenerating one or more hydraulic jets.
 16. The downhole tool of claim11, wherein the radial thrust elements are disposed about at least aportion of a circumference of a sleeve coupled to the nose portion ofthe downhole tool body.
 17. The downhole tool of claim 11, furthercomprising a mechanism for activating the radial thrust elements toapply a radial thrust to the downhole tool.
 18. The downhole tool ofclaim 11, wherein the nose portion includes a sealing element forsealing engagement with the tubular.
 19. The downhole tool of claim 18,wherein a rear portion of the downhole tool body includes a sealingelement for sealing engagement with the tubular.